Variation, adaptation and selection

Learning objectives

Describe variation as differences between individuals of the same species, distinguish continuous variation (a range between two extremes, such as body length and mass) from discontinuous variation (a limited number of phenotypes with no intermediates, such as ABO blood groups), investigate examples of each and relate them to genetic and environmental causes

Describe mutation as genetic change, state that mutation is the way in which new alleles are formed and that ionising radiation and some chemicals increase the rate of mutation, and at Extended describe gene mutation as a random change in the base sequence of DNA and state that mutation, meiosis, random mating and random fertilisation are sources of genetic variation

Describe an adaptive feature as an inherited feature that helps an organism survive and reproduce in its environment, interpret information about a species to describe its adaptive features, and at Extended explain the adaptive features of hydrophytes and xerophytes

Describe natural selection in terms of variation within a population, the production of many offspring, competition and the struggle for survival, and the survival and reproduction of better adapted individuals, which pass on their alleles

Describe adaptation and evolution as the outcome of natural selection over many generations, and describe the development of antibiotic-resistant bacteria as an example of evolution by natural selection (Extended)

Describe selective breeding (artificial selection) by choosing individuals with desirable features, crossing them and selecting from their offspring over many generations to improve crop plants and domesticated animals, and at Extended outline the differences between natural and artificial selection